Abstract: I argue for a theoretical link between the development of an extended period of immaturity in human evolution and the emergence of powerful and wide-ranging causal learning mechanisms, particularly the use of causal models and Bayesian learning. In fact, young children may actually be more wide-ranging and effective causal learners than adults. I argue that, particularly in the course of play, children perform more “high-temperature” searches of hypothesis spaces than adults do. In one empirical study 4 year olds were better able to learn a low probability higher-order causal hypothesis from data than adults were. In a second empirical study preschool children given new information about a causal system made very similar inferences both when they considered counterfactuals about the system and when they engaged in pretend play about it. Counterfactual cognition and causally coherent pretence were also significantly correlated even when age, general cognitive development and executive function were controlled for. In a third study we found that children in pretend play made distinctive “surgical intervention” inferences which they did not make in less playful counterfactual contexts, when they were more likely to make “backtracking” inferences.